This invention is directed to a valve arrangement for selectively distributing fluids from a plurality of supply vessels to a receiving vessel, and in particular to a valve arrangement of the type utilized in chemical apparatus such as a protein sequenator, for effecting selective conveyance and distribution of liquid or gaseous substances from a plurality of substance-storing vessels to a processing vessel. In such conveyance and distribution devices, the successful operation thereof depends on the efficiency with which the substances are completely distributed into the processing vessel.
Accordingly, residues remaining in the dosage lines leading from the shutoff valves to the processing vessel, and the possibility caused by leaky shutoff valves of reagent being distributed to the processing vessel at the wrong time diminish the quantity of the dosage supplied, or become contaminants during successive operations of the valve arrangement. For example, in certain well known protein sequenators either the dosage lines are not washable or they are not easily evacuated (Biocal sequenator), or in the alternative, the dosage lines and/or shuttle valves have sufficient clearance volumes (Beckman-Squenzer) whereby the residues of the substances continually build up. The removal of such reagent residues in the dosage lines and shutoff valves can be achieved by utilizing solvents to wash same, but such washing is less than completely satisfactory due to the requirement of a large quantity of solvents to effect such washing out and the unwanted reactions effected thereby in the processing vessel during successive processing steps.